Machine tools such as an edge grinding apparatus include at least one grinding wheel, at least one rotatable holder for a blank, and at least one CNC device for controlling the grinding of the blank according to selected specification. The CNC machine tool may include a multi-axis, linear (X, Y axis) holder instead of a rotatable holder. In either case, a cutting tool moves relative to the blank or workpiece under the control of a programmable controller, including a computer program.
In a standard CNC glass grinding machine, an operator must adjust the CNC parameters to allow the CNC machine to grind the part where it is located on the machine. This can be a slow process and is difficult for many operators to master. The prior art process requires the operator to grind a part, check the part for even grind then adjust the X, Y and rotation offset parameters on the CNC control to move the CNC program to match the part location.
U.S. Pat. No. 5,588,899 discloses one solution to this problem. The apparatus of this patent is an opto-electronic device for positioning eye glass or spectacle lenses in a CNC grinding device. The opto-electronic detecting device includes a CCD (charge coupled device) camera, a first control unit that includes an electronic picture processing and evaluating system cooperating with a second control unit. The system requires the manufacturer of the lens blank to mark each blank. If the blanks are not pre-marked, a separate marking is necessary.
U.S. Pat. No. 5,956,253 discloses a more recent development which uses a video controlled CNC apparatus for processing blanks such as a glass sheet. The device uses a video camera and monitor to program the path of the grinding wheel. The system requires a CNC machine, video camera, a video monitor, a vision board and software to calculate the offset parameters.